This page describes “eightfold morality of the upavasastha (introduction)” as written by Nagarjuna in his Maha-prajnaparamita-sastra (lit. “the treatise on the great virtue of wisdom”) in the 2nd century. This book, written in five volumes, represents an encyclopedia on Buddhism as well as a commentary on the Pancavimsatisahasrika Prajnaparamita.

Part 2 - The eightfold morality of the upavāsastha (introduction)

Question. – For the lay person (avadātavasana) living at home (gṛhasta), is there not the fourfold morality [of the upāsaka] or are there yet other rules?

Answer. – There is also the “morality of a day-and-a-night” (rātradivasaśīla). If it is observed during the six fasting days (upavāsadivasa) of the month, the merit (puṇya) is immense (apramāṇa).[1] If one pledges (samādadāti) to observe it, during the twelve months [of the year], from the 1st to the 5th of each month, the merit is even greater.[2]

In early Buddhism, the word designated the day preceding the lunar quarters, a sacred weekly day or Sabbath. The early religious communities prior to Buddhism used these days to explain their doctrines (cf. Vinaya, I, p. 101). The Buddhists followed their example and, on the fifteenth day of the lunar fortnight, they held a chapter of the order on which the Dharma was explained (Vinaya, I, p. 103). They also chose one or another of the upavāsa days for the recitation of the Pratimokṣa. During the upavāsa days, the lay adepts (avadātavasana) often took it upon themselves to fast and observe some limitations. This practice is called ‘discipline of a day and a night’ (rātridivaśīla), for it is taken for 24 hours only on the 4th, 6th or 15th days of the month; it is also called eightfold morality (aṣṭāṅgaśīla) for the lay person pledges to observe eight interdictions other than the fast (upavāsa).

Footnotes and references:

The Mppś will explain (p. 835F) the origin of these days of fast. The four fasting days are the 8th and the 14th day of the dark fortnight (kālapakṣa), the 8th and the 15th of the bright fortnight (śuklapakṣa): see Yi tsing, tr. Takakusu, p. 63, 188. But the texts prefer six days of fast per month, the 8th, 14th, 15th, 29th and 30th days: cf. Hiuan tsang, tr. Watters, I, p. 304; Chavannes, Contes, I, p. 24, n. 2; Demiéville, Versions chinoises de Milindapañha, XXIV, 1924, p. 77